I am totally lost on how to do this... can anyone help?
What does it mean? I tried to understand what it means before proof but am totally clueless
@GrahamKemp is correct. The statement says that if P(x) holds for no member of the universe of discourse, then P(a)->Q(a).
The fact that we don't have a def for P(x) or Q(x) is is irrelevant because of the truth-table for the material conditional, which tells us that anytime the antecedent --here P(a)-- is false, the material conditional is true. [Remember, validity in natural logic is about truth preservation it can't help you when you start with a false statement].